The present invention relates generally to an image processor which converts an image with poor resolution into an image with improved resolution.
A conventional group 3 (G3) facsimile apparatus (FAX) adopts to standard resolution, high level resolution and/or fine resolution, the high level resolution having twice as high resolution power in a vertical scanning (abbreviated VS hereinafter) direction as the standard resolution, and the fine resolution having twice as high resolution power in respective horizontal scanning (abbreviated HS hereinafter) and VS directions as the high level resolution. Each picture element (pixel) of the standard resolution has area shown in FIG. 1A of LM1 of 1/8 mm in the HS direction multiplied by LS1 of 1/3.58 mm in the VS direction. Each pixel of the high level resolution has area shown in FIG. 1B of LM1 of 1/8 mm in the HS direction multiplied by of 1/7.7 mm in the VS direction. In addition, each pixel of the fine resolution has area shown in FIG. 1C of LM2 of 1/16 mm in the HS direction multiplied by LS3 of 1/15.4 mm in the VS direction. The degree to which image quality, inversely proportional to the area of a pixel, is improved by these resolutions ascends in this order; the fine resolution, high level resolution, standard resolution.
In the conventional communication system in which a receiver FAX uses a resolution superior to a transmitter FAX the receiver FAX uses, for example, the high level resolution and the transmitter FAX uses the standard resolution, the receiver FAX converting a resolution of image data transmitted from the transmitting FAX into its higher resolution (high level resolution) before the receiver FAX stores the image data in its memory or plots out.
However, the above conventional system has a disadvantage in that the receiver FAX cannot perform an effective smoothing process for smoothing jagged edges of an image and thus the image quality is degraded.